SDLT is one of the most frequently mis-applied property taxes. Many landlords overpay by not claiming all available reliefs (multiple dwellings relief, mixed-use treatment, first-time buyer relief where applicable), while others underpay by miscalculating the 3% surcharge or linked transactions. When HMRC opens an enquiry into an SDLT return — which it has the power to do for up to 9 months after filing (or 21 months for late returns) — the consequences can include significant additional tax, interest, and penalties. This guide covers the filing mechanics, penalty regime, amendment procedure, and HMRC enquiry process.
The 14-Day Filing and Payment Deadline
From 1 March 2019, SDLT returns must be filed and any tax due paid within 14 days of the effective date of the land transaction (FA 2003 s.76(1A)): (a) Effective date: for most property purchases, the effective date is the date of completion — not exchange; for leases, the effective date is the date of substantial performance or grant, whichever is earlier; substantial performance typically occurs on payment of a substantial part of the premium or the first rent, or on taking possession of the property; (b) Who files: the purchaser (buyer) is responsible for filing the SDLT return (SDLT1) and paying the tax; in practice, the buyer's conveyancer handles the filing on their behalf; (c) SDLT1 form: the main return; supplementary forms (SDLT2 for additional parties; SDLT3 for additional land; SDLT4 for leases and complex transactions) may be required; returns are filed electronically via HMRC's online service; (d) Prior to 1 March 2019: the deadline was 30 days — returns completed before the change may show this longer deadline; (e) Zero-rate returns: a return must be filed even where no SDLT is payable — for example, a residential purchase below the nil rate threshold (£250,000 in 2024/25; reverts to £125,000 after 31 March 2025); the filing obligation exists regardless of whether tax is due; (f) Practical checklist: ensure your conveyancer confirms the filing date; request a copy of the filed SDLT1 for your records; confirm payment has cleared within the 14-day window.
- 14-day deadline: SDLT return and payment due within 14 days of the effective date (completion date for most purchases)
- File even if nil tax: a return must be filed for all notifiable land transactions — even where the purchase price is below the nil rate band
- Effective date for leases: the effective date for a lease is the earlier of substantial performance or grant — important for BTL landlords taking commercial leases
- Conveyancer files on your behalf: in practice, your conveyancer handles the electronic filing; but you are responsible for ensuring it is filed on time
- Copy SDLT1: always request a copy of the filed SDLT1 from your conveyancer — it is the primary evidence of your SDLT compliance
SDLT Penalties and Interest
Failure to file or pay SDLT on time triggers automatic penalties and interest: (a) Late filing penalties: (i) up to 3 months late: £100 fixed penalty; (ii) more than 3 months late: £200 fixed penalty; (iii) more than 12 months late: additional tax-geared penalty of 5%, 10%, or 15% of the tax due (depending on whether the failure is careless, deliberate without concealment, or deliberate with concealment); (b) Late payment interest: HMRC charges interest on SDLT paid late at the HMRC late payment rate (Bank of England base rate + 2.5% from April 2025); interest runs from the day after the filing deadline until the date of payment; (c) Minimum £100 penalty: even if the tax due is nil, the £100 fixed penalty applies for a late return; (d) Reasonable excuse: a taxpayer can avoid a penalty if they have a 'reasonable excuse' for the late filing — illness, bereavement, reliance on incorrect HMRC guidance, or other circumstances beyond the taxpayer's control may qualify; the reasonable excuse defence does not apply to the late payment interest; (e) Penalty suspension: in some cases, HMRC may suspend a penalty where the taxpayer agrees to correct the underlying issue — though this is more common for income tax than SDLT penalties; (f) Tax avoidance scheme penalties: where SDLT is underpaid because of an avoidance scheme disclosed under the Disclosure of Tax Avoidance Schemes (DOTAS) regime, higher penalties apply.
- £100 fixed penalty: automatic for returns up to 3 months late — applies even if no tax is due
- £200 fixed penalty: returns over 3 months late
- Tax-geared penalty: over 12 months late — 5% (careless), 10% (deliberate), or 15% (deliberate with concealment) of the outstanding tax
- Late payment interest: runs from the day after the deadline at Bank of England base rate + 2.5% — compounds over time
- Reasonable excuse: illness, bereavement, or incorrect HMRC guidance may constitute a reasonable excuse for late filing; does not excuse late payment interest
Amending an SDLT Return — The 12-Month Window
Mistakes in an SDLT return can be corrected by amendment within 12 months of the filing date: (a) Amendment window: under FA 2003 s.76(3), a purchaser can amend an SDLT return within 12 months of the filing deadline (i.e. within 12 months from the date that was 14 days after the effective date); after 12 months, amendments can only be made by HMRC following an enquiry or, in limited circumstances, by an overpayment relief claim; (b) How to amend: use HMRC's online SDLT service to file an amended return; the amendment replaces the original return; a repayment claim or additional tax payment may result; (c) Common reasons for amendment: (i) initial return did not claim available relief (multiple dwellings relief; first-time buyer relief); (ii) the purchase price was later adjusted on a SDLT clawback event (relief condition not met within 3 years); (iii) additional consideration was identified after filing (e.g. overage or contingent consideration); (iv) incorrect surcharge calculation; (d) Overpayment relief: where the 12-month amendment window has passed and the taxpayer has overpaid SDLT, a claim for overpayment relief can be made under FA 2003 Sch.11A within 4 years of the effective date — the claim must establish that the return was incorrect or SDLT was overpaid; this is the primary route for landlords who missed multiple dwellings relief on past purchases; (e) Voluntary disclosure: where the 12-month window has passed and additional SDLT is owed, prompt voluntary disclosure to HMRC (before they discover the error) typically results in lower penalties.
- 12-month amendment window: amend online within 12 months of the filing deadline — after this, only overpayment relief or HMRC-initiated enquiry adjustments apply
- Multiple dwellings relief: the most common amendment — landlords often miss this on portfolio purchases; claim within 12 months of original filing or via overpayment relief (4-year window)
- Overpayment relief: 4-year window from the effective date to claim overpaid SDLT — used where the 12-month amendment window has expired
- Additional consideration: any post-completion adjustments to the purchase price (overage, contingent consideration) must be reported and may trigger an SDLT amendment
- Voluntary disclosure: where you have underpaid, disclose promptly — voluntary disclosure before HMRC discovery attracts lower penalties
HMRC SDLT Enquiries — Powers, Timeframe, and Response
HMRC has the power to open an enquiry into any SDLT return: (a) Enquiry window: HMRC can open an enquiry into an SDLT return within 9 months of the filing date (FA 2003 Sch.10 para.12) — for returns filed on time; for returns filed late, the window is 9 months from the date of actual filing; (b) Triggers: HMRC enquiries are triggered by: (i) automated risk profiling (where the SDLT computation is flagged as unusual); (ii) use of a relief that HMRC is currently challenging (multiple dwellings relief on mixed-use or unusual properties; group relief); (iii) cross-referencing with Land Registry data on related transactions; (iv) tip-offs or related compliance checks on other taxes; (c) Notice of enquiry: HMRC issues a formal notice of enquiry (Schedule 10 notice) specifying the return under investigation; the taxpayer must respond within the specified time; (d) Information requests: HMRC may issue formal information notices (Schedule 36 Finance Act 2008) requiring the taxpayer to produce documents — failure to comply is a criminal offence; (e) Closure notice: HMRC must issue a closure notice when the enquiry is complete — either accepting the return as filed or issuing a determination of additional tax due; the taxpayer has 30 days to appeal a determination to the First-tier Tax Tribunal; (f) Discovery assessments: where HMRC discovers an SDLT underpayment after the enquiry window, it can issue a discovery assessment — the time limit is 6 years for careless errors and 20 years for deliberate errors.
- 9-month enquiry window: HMRC can open an enquiry within 9 months of the filing date — critical to ensure returns are correct from the outset
- Discovery assessments: HMRC can go back 6 years (careless error) or 20 years (deliberate) outside the enquiry window
- Common enquiry triggers: multiple dwellings relief claims; mixed-use SDLT rates; unusual transaction structures; linked transaction disclosures
- Schedule 36 information notices: HMRC can require production of documents; failure to comply is a criminal offence — instruct a tax specialist immediately on receipt of an enquiry notice
- Appeal route: a determination of additional tax can be appealed to the First-tier Tax Tribunal within 30 days — take specialist advice on the merits of appeal before the deadline
Frequently asked questions
What happens if I miss the SDLT filing deadline?+
If you miss the 14-day filing deadline, HMRC automatically charges a penalty: £100 for returns up to 3 months late; £200 for returns over 3 months late. After 12 months, tax-geared penalties of 5%, 10%, or 15% of the outstanding tax apply depending on whether the failure is careless or deliberate. HMRC also charges late payment interest from the day after the deadline at the prevailing HMRC interest rate (Bank of England base rate plus 2.5%). These penalties apply even if no tax is due — the filing obligation exists for all notifiable land transactions. Contact your conveyancer immediately if you believe a return has been filed late.
Can I still reclaim multiple dwellings relief if I missed it on my original return?+
If your original SDLT return was filed less than 12 months ago, you can amend the return to claim multiple dwellings relief using HMRC's online service. If the 12-month amendment window has passed, you can make a claim for overpayment relief under FA 2003 Schedule 11A — but you must do so within 4 years of the effective date (completion date) of the purchase. Overpayment relief claims are made by letter to HMRC SDLT. Note that HMRC has challenged some multiple dwellings relief claims (particularly on mixed-use or 'garden chalet' arrangements) — specialist SDLT advice is recommended before making a late claim.
How long does HMRC have to investigate my SDLT return?+
HMRC can open a formal enquiry into an SDLT return within 9 months of the date the return was filed (if on time) or within 9 months of the date of actual filing (if late). Outside the enquiry window, HMRC can still issue a 'discovery assessment' if it discovers an error: within 6 years of the effective date for careless errors, and within 20 years for deliberate errors. This means that for a buy-to-let purchase where SDLT was deliberately underpaid, HMRC could investigate up to 20 years later. Always retain all SDLT return documentation, completion statements, and valuation evidence for at least 20 years.
Do I need to file an SDLT return if I buy a property below the nil rate band?+
Yes — an SDLT return must be filed for all notifiable land transactions even if no tax is due. A residential purchase below the nil rate band (£250,000 until 31 March 2025; £125,000 thereafter) is still a notifiable transaction and requires an SDLT1 return within 14 days of completion. The penalty for a late return (£100 fixed penalty) applies even where no tax is payable. The only transactions that do not require a return are those that are non-notifiable — primarily gifts of land where no chargeable consideration is given (and no mortgage is assumed). Your conveyancer should file the return as part of the post-completion process.